How EFFICIENTLY to extract multiple column base on multiple condition

Question

balandong 2017-11-30

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评论： balandong 2017-11-30

Dear all, The objective was extract the data from s.c2. Depending on the binary state (either 1 or 2) of s.state, the data can be extracted either from either column ONE or Two of the s.c2. To achieve the objective, the following code were realized. However, the code is ineffective. In other word, the number of Function (EXTRACT_COL) calling increase with number of COLUMNX.

I wonder if there any possible way to optimize this code further. For example, we can input all the binary state vector and get the respective s.c2 column all at once. That is, do the procedure in parallel.

I really appreciate for any advice or tips.

Thanks in advance

Columnx=10;
s.c2 = randi(10,4,2);
s.state=randi([1  2],1,Columnx);
[r]= arrayfun(@(k)  extract_Col(s,k),1:6,'un',0);
function r=extract_Col(s,x)
col=s.state(x);
r(:,x)=s.c2(:,col);
end

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Answer 1

per isakson 2017-11-30

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编辑：per isakson 2017-11-30

在 MATLAB Online 中打开

Your text make me think you want

r = s.c2(:,s.state)

or possibly

r = num2cell( s.c2(:,s.state) )

but your code does something different

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balandong 2017-11-30

Hi Per, thanks for the quick reply, yes direct indexing is rather straight forward. Really appreciate the time taken to entertain this problem.

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Answer 2

Jos (10584) 2017-11-30

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Why not simply use direct indexing?

r = s.c2(:, s.state)

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balandong 2017-11-30

Hi Jos, Thanks for the quick reply. Yes, I should use direct indexing. Btw, I had to accept Per answer, since he give the 1st answer. Really appreciate your help

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